With the recent increase in hygiene consciousness, an increasing number of people are concerned about their body odor. The term “body odor” is a generic term for the odor or smell generated in various parts of the body, and main sources of the odor or smell include the head, mouth, armpit, groin, and foot sole. Among such sources of the odor or smell, the armpit smell is easily detected by the person himself/herself or by the people in the immediate area of the person, and the factors such as presence/absence, strength, and qualitative difference of the armpit smell greatly affect the systemic body odor. Therefore, it is often the armpit smell and not the body odor in general that is annoying for the person himself/herself or for the people in the immediate area of the person.
The armpit smell comprises a sour and stuffy smell and a smell specifically found in the armpit. The sour and stuffy smell is generated by decomposition of the eccrine sweat and grime secreted by the eccrine gland by the action of the indigenous bacteria of the skin. The main cause of this smell is lower carboxylic acids containing 2 to 5 carbon atoms, and this smell is called a “lower fatty acid smell”, or more simply, an “acid smell”. In contrast, the smell specific to the armpit is generated by decomposition of apocrine sweat secreted from the apocrine gland containing proteins and cholesterol at a high concentration by the action of the indigenous bacteria of the skin, and this smell is called the “apocrine odor” or “armpit smell” (hereinafter referred to as the “apocrine odor”).
Accordingly, for those people who are conscious about their body odor, and in particular, the armpit smell, it would be quite important to know the degree of their apocrine odor that they originally have in their armpit, and whether their own effort of reducing the body odor, for example, by the use of deodorant products or surgical removal of the apocrine gland, actually had some effects.
Conventional methods that have been used in finding the degree (presence or strength) of one's own apocrine odor in the armpit include (1) a sensory test in which the armpit smell is evaluated by a third person, (2) an estimation based on information such as the presence of a person with the armpit smell in his or her family and moist cerumen, and the like which are said to be related to the apocrine odor.
However, the method (1) is associated with the difficulty of a quantitative assessment due to the large margin of the subjective decision of the panelist and assessment error due to olfactory fatigue. In the meanwhile, the method (2) does not directly assess the apocrine odor in the armpit, and this method cannot be used in an objective and quantitative determination of the effectiveness of the improvement of the armpit smell by the use of deodorant products or the effect of the surgical removal of the apocrine gland.
Conventional methods that have been used to determine the effectiveness of the deodorant which is expected to suppress the apocrine odor generation include (1) a method in which the candidate deodorant is applied to the armpit of the test subjects, and the smell of the armpit is evaluated after the application, and (2) a method in which the candidate deodorant is mixed with the sweat collected from the armpit of the test subject, and the smell of the mixture is evaluated after an adequate incubation of the mixture.
Both of these methods, however, are associated with the considerable burden of the test subjects and this leads to the difficulty of evaluating a large number of candidate deodorants under the same conditions. In addition, quantitative assessment is difficult due to the large margin of the subjective decision of the panelist and assessment error due to olfactory fatigue. Furthermore, such method is associated with the difficulty in differentiating whether it was the generation of the apocrine odor that was suppressed by the candidate deodorant; whether the apocrine odor that had been generated was deodorized; or whether the apocrine odor was sensed to a lower degree by the presence of another odor. Accordingly, an accurate, efficient, objective, and quantitative determination of the “effectiveness in suppressing the apocrine odor generation” has been difficult.
The inventors of the present invention investigated odor components in the human armpit, and found that the main components responsible for the apocrine odor are alcohol compounds having a thiol group at position 3 (hereinafter sometimes referred to as 3-mercapto alcohol compound) as typically represented by 3-mercapto-3-methylhexane-1-ol, 3-mercaptohexane-1-ol, 3-mercaptopentane-1-ol, 3-mercapto-2-methylbutane-1-ol, and 3-mercapto-2-methylpentane-1-ol (Non-patent document 1).
The inventors of the present invention also found that 3-mercapto-3-methylhexane-1-ol is present at a mass ratio of 10 or more times higher than that of other 3-mercapto alcohol compounds, and that this 3-mercapto-3-methyl-hexane-1-ol is the most common 3-mercapto alcohol compound in the armpit of people having apocrine odor (Non-patent document 1).
The inventors of the present invention also found that the 3-mercapto-3-methylhexane-1-ol is an optically active substance comprising 72% by mass of (S)-3-mercapto-3-methylhexane-1-ol and 28% by mass of (R)-3-mercapto-3-methylhexane-1-ol (Non-patent document 1)
Patent Document 1 discloses that, as flavoring components, 3-mercapto-2-methylbutane-1-ol has the characteristic odor like grass, leek, or gas, (S)-3-mercaptohexane-1-ol has a grass or rustic odor, and (R)-3-mercaptohexane-1-ol has odor like a grapefruit/passion fruit, gooseberry, or onion.
[Non-patent document 1] Japanese Journal of Taste and Smell Research, vol. 10, No. 3, pages 807-810 (December 2003).
[Patent Document 1] JP-A-2001-2634.